This invention relates to a labeler and more particularly to a continuously moving web pressure-sensitive labeler. Still more particularly, this invention is an important improvement over the labeling system of prior U.S. Pat. No. 4,842,660 which issued Jun. 27, 1989, on application Ser. No. 225,669 filed Jul. 27, 1988, in the names of Helmut Voltmer (one of the present inventors), Alfred F. Schwenzer and Anthony Freakes. Application Ser. No. 225,669 was a continuation of abandoned application Ser. No. 045,315 filed May 4, 1987, which in turn was a continuation of application Ser. No. 845,524 filed Mar. 28, 1986, now U.S. Pat. No. 4,687,535 which issued Aug. 18, 1987. Prior U.S. Pat. Nos. 4,687,535 and 4,842,660 are commonly assigned herewith.
In the labeling system disclosed by the aforesaid prior U.S. Patents, pressure-sensitive labels are applied to articles or containers at a label-applying station. Labels are carried initially by a web, and the system comprises a supply spindle which supports a supply roll including the web carrying the labels thereon. The articles to be labeled are continuously advanced in a given direction past the label-applying station, and the web with the labels thereon is advanced continuously from the supply spindle. Labels are stripped from the web at a label pick-up station and the stripped labels are placed on a vacuum drum that continuously advances the stripped labels in the given direction to meet the articles at the label-applying station. The speed of advance of the articles and the speed of advance of the web are sensed continuously and the speed of advance of the web is adjusted as necessary to match the speed of advance of the articles.
A pressure-sensitive labeler with an intermittently moving web enables good control of the tension in the web, in order to (1) prevent web slack at the rewind roll, (2) guarantee good tracking of the web, (3) have the right tension over the peel plate o (where labels are stripped from the web), (4) avoid web breakage and (5) provide enough freedom of the web to be able to bring labels up to the desired speed of the products being labeled.
Tension control thus is very important in obtaining good web flow. The desired tension to meet these five requirements is not always possible because of speed and strength of the web paper. When a compromise is necessary, registration is affected. As used herein, "registration" refers to accuracy in placing a label in a desired location on a product.
Another important feature of a pressure-sensitive labeler with a continuously moving web is the capability of matching accurately label speed with product speed at the label-applying station. If this matching of speed is not accurate, registration will be off.
The aforesaid prior U.S. Patents disclose driving a continuously moving web by a constantly driven feedroller engaging one side of the web with a lift roller engaging the other side of the web directly opposite the feedroller, so that in normal operation the feedroller and the lift roller bight the web directly opposite the feedroller and the lift roller is movable out of engagement with the web to a retracted position to activate a brake, causing the brake to engage and stop the web. The engagement of the feedroller with the web is essentially tangent where a lift roller is used.
Another known means for driving an intermittently moving web utilizes a stepping motor which permits greater circumferential engagement or wraparound of the web with the feedroller and hence more traction to overcome web tension. However, the step increments are too great for fine registration and speed is a limitation.
A further known means for driving an intermittently moving web utilizes a clutch and brake which gives more wraparound of the web on the feedroller than is obtainable with a light roller, but the clutch and brake means are subject to clutch slippage due to varying tension, causing registration problems.
With a continuously moving web, tension control is needed only in peeling labels from the web at a peel plate, and for tracking. Tracking a continuously moving web is easier than tracking a web that comes to rest intermittently.
Further, in the system of the aforesaid prior U.S. Patents, a vacuum drum is rotated at a linear speed that is greater than the speed at which labels are delivered to the outer surface of the drum, so that the outer surface of the drum slips on each label with vacuum being applied to a vacuum passage at a label pick-up station, so that vacuum picks up each label whereby labels are spaced uniformly on the drum from the label pick-up station to the label applying station.
It is an important object of the present invention to provide a continuously moving web pressure-sensitive labeler with much improved label pitch flexibility and control.
Another important object of the invention is to provide such a continuously moving web pressure-sensitive labeler which enables complete control of label pitch over an infinite continuum of possible label pitches.
An additional important object of the invention is to provide such a labeler which reduces tearing of the web.
The foregoing and other objects and advantages of the invention will appear more clearly hereinafter.